Conventionally, upon manufacturing a semiconductor component or a flat panel display, etc, a substrate such as a semiconductor wafer or a liquid crystal substrate is subjected to various processes using a liquid processing apparatus in order to perform a cleaning process or etching process.
In this liquid processing apparatus, a process using a deionized water has been widely performed for a process such as a cleaning of the substrate, but since the deionized water has a high specific resistance value, a static electricity is generated while the substrate is processed with the deionized water, and thus there have been caused such problems that the electrostatic breakdown can be generated at the surface of the substrate by the static electricity or particles can be adhered to the surface of the substrate.
In view of these problems, the liquid processing apparatus is provided with a processing liquid generating unit for generating a processing liquid by dissolving a gas such as carbon dioxide or ammonia gas into the deionized water. As a result, the processing liquid generated by the processing liquid generating unit has a low specific resistance value, and is used to process a wafer.
And, a conventional liquid processing apparatus is provided with a processing liquid generating unit 101 configured as shown in FIG. 5. In processing liquid generating unit 101, a gas dissolving line 103 and a bypass line 104 are connected in parallel to a deionized water source 102 for supplying the deionized water, a gas dissolver 105 is provided in an intermediate part of gas dissolving line 103, and a gas source 106 for supplying a gas such as carbon dioxide or ammonia gas is connected to gas dissolver 105.
The processing liquid generating unit 101 is configured to dissolve the gas into the deionized water flowing through gas dissolving line 103 by gas dissolver 105 and then to mix the deionized water with a deionized water flowing through bypass line 104, and thus to generate a processing liquid having a specific resistance value reduced to a predetermined value. See, for example, Japanese Patent Laid-open No. 2000-159504.
The processing liquid generating unit 101 is configured to dissolve the gas into the deionized water flowing through gas dissolving line 103 by gas dissolver 105 and then to mix the deionized water with a deionized water flowing through bypass line 104, thereby generating a processing liquid which has a predetermined concentration by reducing the specific resistance to a predetermined value.
In this way, the conventional liquid processing apparatus is caused to generate a processing liquid having a predetermined concentration (a predetermined property) regulated by dissolving a gas such as a carbon dioxide into a solvent such as a deionized water and to process a substrate at one of substrate processing units or simultaneously at two or more of the substrate processing units using the processing liquid.
However, it is often the case that since the conventional liquid processing apparatus is configured to process a substrate at one of a plurality of substrate processing units or simultaneously at two or more of the plurality of substrate processing units, the flow rate of the processing liquid used at a time, that is, the flow rate of the processing liquid generated by the processing liquid generating unit is largely fluctuated depending upon the number of the substrate processing units used simultaneously. Especially, there has been a problem that if the flow rate of the processing liquid (the flow rate of processing liquid generated by the substrate processing unit) is reduced, the processing liquid may not be generated with a desired concentration (specific resistance value) by the processing liquid generating unit.